As we said in our section on the "Speaker," we don't know much about our speaker, but it's clear that he likes to be out and about at night. Every section of the poem, whether cheerful or creepy, takes place after the sun has gone down. Though the setting remains pretty much the same – it's always dark out – the mood of the poem really changes. You know how you can be out alone at night feeling all happy, but then in a split second you can get freaked out and have the unreasonable fear that someone is totally following you? "The Bells" is like that – same setting, but the feel completely changes.
Maybe we've been watching too many vampire movies lately, but we think this poem could really be a vampire horror flick. In movies where vampires take over the world (you can substitute zombies here, if that's more your speed), things usually seem just fine at first. People are hanging out, taking sleigh rides, whatever it is they do. Then things go wrong. There's a ton of noise, and then a lot of fear, and finally, death. Check it out: the story arc in "The Bells" is pretty much the same. Now, read this poem again and imagine some vampires lurking. It kind of fits, right?